ANTLEE BIOTH. 23 



taking advantage of their habit of migration. They are found to 

 object greatly to burnt surfaces, and to move off rapidly where the 

 travelling parties come on fired ground. This plan therefore might 

 apparently be serviceable in checking advance where their presence 

 was likely to be especially injurious ; also it might be used for directing 

 the moving caterpillars to where by natural or artificial means they 

 may be destroyed. A mountain stream is a most convenient place for 

 their course to be directed to (see p. 20), or a pool, or a pit with water 

 at the bottom, or deep ditches may be made. If full of water they 

 will destroy great numbers, but a dry hollowed-out space or kind of 

 broad ditch may also be made to serve well ; it is said that by driving 

 sheep to and fro where the grubs are thus collected in a narrow space 

 whilst on their travels great numbers may be destroyed. The same 

 treatment, or any kind of treatment which would crush them, would 

 be equally applicable in cases where (see p. 15) they were seen in great 

 bodies going down the hill-paths, or where, as in the great infestations 

 of 1816 and 1817, the roads, and more especially the ruts in the roads, 

 in the Hartz district were so filled with the caterpillars that their 

 crushed bodies made the way dirty and slippery. 



Driving pigs on the infested ground is a measure particularly 

 advised for clearing the caterpillars, and doubtless would do well 

 where it was practicable, but this would by no means be so in all cases. 

 Probably where weather and the various circumstances allowed, the 

 best preventive of recurrence would be well-directed firing of whatever 

 infested land the treatment could properly be applied to, as in the case 

 of the Glamorganshire attack of 1884 (before alluded to), in which 

 special mention was made of the localities of attack being noticeable, 

 when standing on the ridge of the Ogmore Valley, by the smoke of 

 the mountain fires which were seen to the west, where attempts were 

 being made to destroy the pests ; in this case presumably effectual, as 

 no further reports were sent of presence. 



